AIMs: a new strategy to control physical aging and gas transport in mixed-matrix membranes

The effect of controlling interactions between the components in a mixed-matrix membrane at the molecular level has been explored. A systematic series of soluble metal-organic polyhedra (MOPs) of varying external organic chain length were prepared and applied within polymer membranes to produce anti-aging intercalated membranes (AIMs). Use of a soluble porous additive allowed for intimate mixing between the polymer and the porous additive, eliminating the formation of non-selective gas transport voids at the interface, typically found in traditional mixed-matrix membranes. Moreover, the molecular interaction thus created provided a valuable tool for tailoring the physical aging rates of the membranes. Aging was slowed by a factor of three with the optimal tBu-MOP additive, and viscosity measurements revealed they held the strongest MOP-polymer interaction, confirming the utility of the AIMs approach. MOP loading was therefore able to be optimized for the maximum anti-aging effect by monitoring the relative change in viscosity. Absolute gas permeability scaled with the MOP external organic chain length, revealing solubility-driven diffusion.